Electric charging systems



May 5, 1959 C. 'W. STAUFENBKERG, JR

ELECTRIC CHARGING SYSTEMS Filed Aug. 6, 1956 United States Patent O 2,835,623 ELECTRIC CHARGING SYSTEMS Charles W. Staufenberg, Jr., Glen Ellyn, Ill., assignor to Raytheon Manufacturing Company, Waltham, Mass., a corporation of Delaware Application August 6, 1956, Serial No. 602,952 14 Claims. (Cl. 320-45) This invention relates to an electric charging system, and, in particular, to a system for controlling the voltage to which a storage device is charged.

It is often economically practical and desirable to charge a storage device, such as a battery, which has become depleted in order to continue its useful life. Electric charging systems for charging a battery preferably include voltage or current-sensitive devices in order to prevent damage to the battery by excessive charging current. The present invention discloses a novel system for charging a battery to a safe terminal voltage, and, when the proper terminal voltage is reached, the source of charging current is rendered inoperative. A sensing circuit or control circuit, which renders the current source inoperative at the proper value of terminal voltage, includes a semiconductor device, such as a transistor. The unique characteristics of the semiconductor device are readily adaptable to the requirements of the control circuit employed, and the overall simplicity and sensitivity of the system makes the invention an improvement in the art of electric chargers.

In accordance with the present invention, a charging current is provided and can be coupled to the terminals of a battery to be charged. The terminal voltage of the battery is continuously sampled by a control circuit, which compares said terminal voltage to a preselectable reference voltage. A semiconductor amplier circuit provides current for energizing a current-sensitive device whenever a predetermined variation exists between said terminal and reference voltages; said reference voltage is selected to be a safe value to which the battery can be charged. When the terminal voltage of the battery reaches a predetermined voltage, said current-sensitive device removes the charging current. In this manner, the battery is controllably charged to a safe value of terminal voltage.

Hereinafter, for the purpose of uniformity and understanding, it will be understood that the word battery may be comprised of one or a plurality of cells capable of storing electrical energy.

Other and further objects and attributes of the system may be had from the following description when taken in conjunction with the accompanying drawing, wherein the single gure depicts in semi-schematic diagram form an embodiment of the invention.

Referring now to the drawing, a primary winding of an iron-core transformer 11 has one terminal thereof connected to a contact of a pair of normally open contacts 12 of an initiation switch 13. Another contact of the "contacts 12 is connected to a terminal 14 through aj protective fuse 15. Another terminal of the primary winding 10 is connected to a terminal 16. The terminals 14 and 16 are, in turn, connected to an alternating current source (not shown), which energizes the primary winding when the contacts 12 are closed. It will be understood to those persons skilled in the art that the Vcontacts 12 are ganged, as shown by a broken line 17,'to1a pair of normally closed contacts 18 to be described subsequently. In addition, the initiation switch may preferably be of the type wherein the contacts 12 can be closed manually, causing the contacts 18 to open, but said contacts 12 and 18 are returned to their normal positions after a short delay. A pair of normally open contacts 19 of a relay 20 is shunt connected across the contacts comprising the contacts 12 for maintaining said primary winding energized after the contacts 12 open again. Another pair of normally closed contacts 21 of the relay 20 is subsequently described.

A secondary winding 22 of the transformer 11 is energized by the primary winding 10. A direct current source 23 is attached across the secondary winding 22 and is energized thereby to generate current for charging a storage device, such as a battery 24 or a plurality of series-connected batteries, at a safe, controllable rate of current. lt will be understood that the D.-C. source 23 may be comprised of diode rectiers connected across the secondary winding7 22 as full wave rectifiers causing current to pass through a current-limiting resistor 25 from a center tap 26 on each half cycle of the alternating current applied to the secondary winding 22. A positive terminal 27 and a negative terminal 28 of the battery are connected between the D.C. source 23 and the center tap 26 for charging said battery.

Another secondary winding 29 of the transformer 11 is energized by the primary winding 10. A direct current source 30 is attached across the secondary winding 29 and is energized thereby. This D.C. source may pref erably be regulated, and, therefore, said D.C. source 30' may be comprised of a diode rectifier, a filter capacitor, and a gaseous voltage regulator discharge valve, or other components arranged in a manner already known to those persons skilled in the art for generating a D.C.' voltage of the polarity shown acnoss a voltage divider 31, connected thereto. The voltage divider may be comprised of serially-connected resistors 32 and 33. The resistors are preferably selected to apply a proper negative potential between the elements of a semiconductor device 34. A collector 35 and an emitter 36 are connected across the resistor 33 through a solenoid or control win-ding 37 of the relay 2i). A filter capacitor 38 is attached between a base 39 and the emitter 36. In the embodiment of the invention illustrated, a PNP type transistor is employed. However, it is understood and realized that other types of transistors can be used with the proper polarity of energizing voltages. A second voltage divider 40 is shunt connected across the D.-C. source 3G. This voltage divider is comprised of the variable resistor 41 and resistors 42 and 43 serially connected. Adjustment of the variable resistor 41 is employed to preselect the value of a reference voltage across the resistor 43, which is applied to the emitter 36 by a lead fili connected between the positive termi-y nal of the voltage divider 4i) and said emitter. A cornmutative capacitor 45 has one end thereof connected to a negative potential 45 of said voltage divider 40 and another end connected to said base 39. The positive terminal 27 of the battery 24 is coupled via a resistor 47 to the base side of the capacitor 45 and the negative terminal 28 is tied directly to the negative potential 46. In this manner, the terminal voltage of said battery is applied to the capacitor 45. The reference voltage is selected to be a safe value below a maximum value to which the cells comprising a battery can be charged for reasons subsequently explained.

A suppression circuit 48, shunt connected across the resistor 43, comprised of' a loading resistor 49, the normally closed switch contacts 1S and the normally closed relay contacts 21 serially connected, primarily serves to connect the resistor 49 in shunt with said resistor 43 when the relay 20 is deenergized. This circuit is a precautioni` ary 'device to prevent the reference voltage from rising and causing the amplifier to conduct after the relay 20 becomes deenergized, and is especially needed when a gaseous `voltage regulator discharge valve is employed to regulate the D.-C. source 30.

' In one embodiment of the invention, four series-connected silver-zinc cells comprising the battery were connected to the appropriate terminals and charged. Characteristically, one of these cells is completely charged when its voltage, while charging, is 2.00il.5% while the maximum permissible voltage at which a cell is charging is 2.10 volts. Thus, a fully charged battery, consisting of said four cells while charging, has a terminal voltage between 7.88 and 8.12 volts and it follows that the maximum safe voltage of the battery is 8.40 volts. The D.-C. source 30, the semiconductor device 34 and the components previously mentioned as connected thereto have been arranged to form a differential voltage control circuit; said lcircuit controls current for energizing the relay 20 when the output of the battery is less than a predetermined value. Stated otherwise, said semiconductor device amplies the diterence voltage between the preselected reference voltage and the terminal voltage of the lbattery until said terminal voltage reaches a predetermined value. In the embodiment being described, the reference voltage was adjusted to 8.0 volts and the amplitier was adjusted so as to be unable to handle a suliicient magnitude of current for energizing said relay 20 when the terminal voltage reached 7.88 volts.

Assuming a battery 24 of the silver-zinc cell type men-v tioned is connected to the appropriate terminals, closing the lswitch 13 initiates the charging of said battery and the operation of said control circuit. The charging rate was Selected to be approximately two amperes. The relay 2f? is energized by current flowing through said semiconductor device 34 as long as the base 39 is more negative than the emitter 36 and the difference between the reference and terminal voltages exceeds 0.12 volt. When saidrelay is energized, the primary winding is connected to the terminals 14 and 16 through the contacts 19 and the charging and control circuits are operative. However, when the battery voltage reaches 7,88 volts, the current generated by said semi-conductor 34 is insufficient to keep said relay energized and said normally open contacts 19 return to the open position and the charging D.-C. source 23 is rendered inoperative. Furthermore, the energizing and reference voltages coupled to said semiconductor device are removed by the opening of said contacts 19 while the resistor 49 is connected in shunt with the resistor 43 for the reason given previously by the closing of the contacts 2l.

In essence, what has been described is a novel system for charging a battery or a plurality of series-connected batteries with a safe magnitude of current at a predeter-l mined rate, while a control circuit continuously samples the terminal voltage of the battery and at a predetermined safe voltage renders said charging circuit inoperative. This system is sensitive to voltage changes and exhibits the usual advantageous characteristics of devices employing semiconductor devices.

It is foreseeable that many other configurations of the invention and uses for the invention will suggest themselves to persons skilled in the art based upon the arrangement and principles disclosed herein. Accordingly,

it is desired that the invention not be limited to the polar-v ity of voltages nor to the particular semiconductor device employed herein. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. In combination, a first source of unidirectional current for charging a storage device, a second source of unidirectional current, means connected to said second current source for producing energizing voltages and a reference voltage, means for sampling the terminall voltage of said storage device, means responsive to and connected to said voltage producing means and responsive to and connected to said sampling means for controlling current as a function of a predetermined voltage variation between said reference voltage and said sample voltage, and means connected to said second current source and to said current controlling means and responsive to a predetermined magnitude of current for interrupting said charging current source, whereby the storage device is controllably charged to a predetermined voltage.

2. In combination, a iirst source of unidirectional current for charging a storage device, a second source of unidirectional current, means shunting said second source for producing energizing voltages and a reference voltage,

means for sampling the terminal voltage of the storage device by attachment in shunt therewith, means responsive to and connected to said voltage producing means and responsive to and shunt connected to said sampling v Y means for controlling current as a function of a predeter:

mined voltage variation between said reference voltage and said samplevoltage, and means connected to said iirst and second sources and responsive to and connected to, said current-controlling means for rendering said first and second sources inoperative at a predetermined-magynitude ofncurrent, whereby the storage device is controllably charged to a predetermined voltage.

3. In combination, a first source of unidirectional current for charging a storage device, a second source ofl unidirectional current, means shunting said second source. for producing energizing voltages and a reference voltage, means for sampling the terminal voltage of the storagede?l vice by attachment thereto, means including a semiconductor device responsive to and connected to said voltage to said first and second sources producing means and responsive to and connected to said sampling means for controlling current as a tune-v tion of a-predetermined variation between said referencey voltage and said sample voltage, and means connected' and responsive toancl connected to said current controlling means for rendering said first and second sources inoperative at a predeter-I mined magnitude of current, whereby the storage devicey is controllably charged to a predetermined voltage.

4. In combination, a first source of unidirectional current for charging a storage device, a second source of unidirectional current, means shunting said second source for producing energizing voltages and a reference voltage, means for sampling the terminal voltage of the storage device by attachment in shunt therewith, meansv including a semiconductor device having a collector, aul emitter, and a base responsive to and connected'to said". voltage producing means and responsive to'and connectedY to said sampling means for controlling current as a func-.- tion of a predetermined variation between said reference, voltage and said sample voltage, and means connected to said first and second sources and responsive to and, connected to said current controlling means for renderingsaid irst and second sources inoperative at a predetery, mined magnitude of current, whereby the storage device is controllably charged to a predetermined voltage.

5. In combination, a first source of unidirectional curI rent for charging a storage device, a second source ofv unidirectional current, a current sensitive device con-,` nected to said first and second sources for controlling the operating periods of saidsources, means connected, to said current device for controlling the energized and, deenergized periods of said current device including asemiconductor having a collector, an emitter, and a base,- said collector being connected to a terminalof said cur-.j rent device, means connected to said second source and,Y in shunt between another terminal of said current deviceand said emitter for rendering said emitter more positive than said collector, means connected between said` base and said emitter for sampling the terminal voltage4 of the storage device by attachment in shunt therewith* and means connected to said second source and to v.saicl emitter for producing a reference voltage to render said emitter more positive than said base, whereby the storage device is charged until a predetermined variation exists between said sample voltage and said reference voltage and said sources are rendered inoperative thereafter.

6. In combination, a first source of unidirectional current for charging a storage device, a second source of unidirectional current, means shunting said second source for producing energizing voltages and a reference voltage, means including a capacitor for sampling the terminal voltage of the storage device by attachment thereto, means including a semiconductor device responsive to yand connected to said voltage producing means and responsive to and connected in shunt with said capacitor for controlling current as a function of a predetermined variation between said reference and said sample voltages, and means connected to said tirst and second sources and responsive to and connected to said current controlling means for rendering said first and second sources inoperative at a predetermined magnitude of current, whereby the storage device is controllably charged to a predetermined voltage.

7. In combination, a first source of unidirectional current for charging a storage device, a second source of unidirectional current, a capacitor for sampling the terminal voltage of the storage device by attachment thereto, means shunting said second source for producing energizing voltages and a reference voltage, means including a semiconductor device having a collector, an emitter, and a base responsive to and connected to said voltage producing means and responsive to said sample voltage connected between said base and emitter for controlling current as a function of a predetermined variation between said reference and said sample voltages, and means connected to said first and second sources and responsive to and connected to said current controlling means for rendering said first and second sources inoperative at a predetermined magnitude of current, whereby the storage device is controllably charged to a predetermined voltage.

S. In combination, a first source of unidirectional current for charging a storage device, a second source of unidirectional current, means for sampling the terminal voltage of the storage device by attachment in shunt therewith, a voltage divider shunting said second source for producing an energizing voltage and a reference voltage, means including a semiconductor device, having a collector, an emitter, and a base, connected to said voltage divider for energizing said collector and said emitter with said energizing voltage and for biasing said emitter with a reference voltage and responsive to sample voltage connected between said base and emitter for controlling current as a function of a predetermined variation between said reference voltage and said sample voltage, and means connected to said first and second sources and responsive to and connected to said current controlling means for rendering said first and second sources inoperative at a predetermined magnitude of current, whereby the storage device is controllably charged to a predetermined voltage.

9. In combination, a first source of unidirectional current for charging a storage device, a second source of unidirectional current, means shunting said second source for producing an energizing voltage, a voltage divider shunting said second source for producing a reference voltage, current controlling means including a semiconductor device, having a collector, an emitter, and a base, connected to said voltage producing means for energizing said collector and emitter and connected to said voltage divider for biasing said emitter with said reference voltage, means connected between said base and emitter for sampling the terminal voltage of said storage device, whereby said semiconductor controls current as a function of a predetermined variation between said reference voltage and said sample voltage, and means connected to said first and second sources and to said current con trolling means and responsive to a predetermined magnitude of current for rendering said first and second sources inoperative, whereby the storage device is charged to a predetermined voltage.

10. In combination, a first source of unidirectional current for charging a storage device, a second source of unidirectional current, a first voltage divider shunting said second source, a second voltage divider shunting said second source, current controlling means including a semiconductor device, having a collector, an emitter, and a base, a filter capacitor connected between said base and emitter, said collector and said emitter connected to said first voltage divider ina manner causing said emitter to be more positive than said collector, means connected between said base and voltage of the storage device, said emitter being connected to said second voltage divider in a manner so as to bias said emitter biased with a reference voltage, whereby said semiconductor controls current as a function of a predetermined variation between said reference voltage and said sample voltage, and means connected to said first and second sources and to said current controlling meansV and responsive to a predetermined magnitude of current for rendering said first and second sources inoperative,.whereby the storage device is charged to a predetermined value.

1l. In combination, a first source of unidirectional current for charging a storage device, a second source of unidirectional current, means connected to said first. and second sources for energizing said sources, means shunting said second source for producing energizing voltagesk and a reference voltagemeans for sampling the terminalA voltage of the storage device by attachment thereto, means including a semiconductor device responsive to and connected to said voltage producing means for controlling current as a function of a predetermined variation between said reference voltage and said sample voltage, and means connected to said energizing means and responsive to and connected to said current controlling means for rendering said first and second sources inoperative at a predetermined magnitude of current, whereby the storage device is controllably charged to a predetermined voltage.

l2. In combination, a charging source of unidirectional current, means for coupling said source to the terminals of a storage device, means shunt connected to said source for producing energizing and reference voltages, means for sampling the terminal voltage of the storage device, means including a semiconductor device responsive to and connected to said voltage producing means and responsive to and connected to said sampling means for controlling current as a function of a predetermined variation between said reference voltage and said sample voltage, means connected to said source for energizing said source, and means connected to said energizing means and to said current controlling means for rendering said source inoperative at a predetermined magnitude of current, whereby the storage device is charged to a predetermined voltage.

13. In combination, a source of unidirectional current for charging a storage device, a regulated source of unidirectional current, rneans shunt connected to said regulated source for producing an energizing voltage, current generating means including a semiconductor device, having a collector, an emitter, and a base, a filter capacitor connected between said emitter and said base, a current sensitive device including a control winding and a pair of normally open contacts and a pair of normally closed contacts, said control winding being connected between said voltage producing means and said collector, said emitter being connected to said voltage producing means in a manner to render said emitter more positive than said collector, means shunt connected to said regulated source including a plurality of resistance components for proemitter for sampling the terminal ducin'g-'-a`refe'rence" voltage across a resistive component, said emitter` being -connected to said resistive component, means connected between said base and a more negative side of said resistive component than' said emitter 'for sampling the terminal voltage of the storage device, means for coupling said sampling means to the terminals of the storage device, an alternating current source, means including said normally open contacts shunt connected across said alternating current source and having outputs connected to said sources for controlling the operative periods of said sources, and means including a loading device and said normally closed contacts serially connected and shunt connected across said resistive component for suppressing spurious operation of said current generating means, whereby the storage device is charged to a predetermined terminal voltage while va predetermined variation exists between said terminal and reference voltages and said sources are rendered inoperative and said loading device is shunted across said resistive component after the storage device is charged.

14. In combination, a source of unidirectional current for charging a storage battery, a source of regulated unidirectional current, a rst voltage divider shunting said regulated source, a relay including a solenoid and a pair of normally open and a pair of normally closed contacts, a semiconductor device including a collector, an emitter, and a base, said collector being serially attached to a negative potential of said rst voltage divider through said solenoid, said emitter being attached to a more positive potential .of said rst voltage divider, a second voltage divider shunting said regulated source including a plurality of resistive components and having means for varying a reference voltage developed across one resistive component thereof, a lter capacitor connected between said 8 base and said emitter, a commutating capacitor having one end thereof connected to said base and another end connected to a negative side of said resistive component, said emitter being attached to a positive side of said resistive component, means for coupling the terminals of the storage device to the ends of said commutating capacitor, an energizing circuit for said D.C. sources including an alternating current source, a fuse, a transformer having a primary and a plurality of secondary windings, and an initiation switch having a pair of normally open and a pair of normally closed contacts, said primary winding being connected to and responsive to said alternating current source when said normally open switch contacts are closed, said secondary windings being connected tol said D.C. voltage sources and responsive to said primary winding Afor energizing said sources, said normally open relay contacts being shunt connected across said normally open switch contacts, a suppression circuit shunting said resistive component including a loading resistor and saidv normally closed switch and relay contacts serially con-. nected, whereby said semiconductor device generates su cient current to energize said relay when the variation between the terminal voltage and said reference voltage is a predetermined value, and said relay deenergizesafter the storage device is charged, loading said emitter circuit.

References Cited in the le of this patent UNITED STATES PATENTS 746,140 `Owens Dec. 8, 1903 1,275,586 Mount Aug. 13, 1918 2,563,659 Parington Aug. 7, 1951 2,675,515 Blasheld Apr. 13, 1954 2,763,820 Fiedler Sept. 18, 1956 

